1. Field of the Invention
This invention relates to water resistant compositions, especially suitable as compositions for treating inorganic materials and defogging compositions.
2. Description of the Prior Art
Heretofore, polyvinyl alcohol (hereinafter referred to as PVA) has been widely employed as various binders, adhesives or surface treating sizing agents and is known to possess excellent performance in film forming properties and strength far superior to any other sizing agent. However, since PVA is water soluble, it has a disadvantage that its water resistance is poor, and therefore various methods have heretofore been studied for the purpose of improving it, but up until the present time no satisfactory method had yet been obtained.
For example, Japanese Patent Application Laid-open No. 123189/1975 (U.S. Pat. No. 4,219,591) describes that a modified PVA having a silyl group in the molecule, is effective as a coating agent for inorganic silicate substrates such as glass etc. However, as can be understood from the comparative example described hereinafter the modified PVA alone cannot impart adequate water resistance.
Transparent materials such as plastic materials, inorganic glass etc. are in general widely utilized as window glass for buildings, vehicles, aircrafts etc., mirrors, spectacle lenses, goggles, agricultural films, food wrapping films etc. These transparent materials have the disadvantage that under highly humid conditions or at a temperature below the dew point, atmospheric moisture condenses on the surface, thereby fogging the surface. In the case of a plastic material, there is the disadvantage that the surface easily gets scratched and tends to bring about a reduction in transparency.
Various attemps for preventing such a phenomenon and imparting defogging properties and scratch resistance to the surface of transparent materials have heretofore been proposed. For example, in order to improve the water wetting properties of the surface of transparent materials, a method which comprises coating a surface active agent such as glycerin, polyalkylene glycol, cellulose derivative, polyvinyl alcohol, polyhydroxyalkyl acrylate, polyethyleneimine or the like has been proposed. This method, although being able to temporarily impart defogging properties, had the disadvantage that the defogging properties were reduced with time, due to leakage of the defogging agent, to the fact that the scratch resistance was not enough, and so forth. Japanese Patent Application Laid-open Nos. 39347/1978, 99987/1980, 73059/1982 etc. discloses methods for forming a defogging film which comprise using a composition mainly comprising either a hydrophilic polymer such as PVA etc. and silica, or these two further combined with a lower molecular weight organic silicon compound. However, the defogging films formed by these methods have the disadvantage that upon water absorption the surface hardness was low and easily bringing about scratches by, e.g., nails, and thus being far from practical.